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srsChEstimatorUnittest.m
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srsChEstimatorUnittest.m
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%srsChEstimatorUnittest Unit tests for the port channel estimator.
% This class implements unit tests for the port channel estimator functions using
% the matlab.unittest framework. The simplest use consists in creating an object with
% testCase = srsChEstimatorUnittest
% and then running all the tests with
% testResults = testCase.run
%
% srsChEstimatorUnittest Properties (Constant):
%
% srsBlock - The tested block (i.e., 'port_channel_estimator').
% srsBlockType - The type of the tested block, including layer
% (i.e., 'phy/upper/signal_processors').
%
% srsChEstimatorUnittest Properties (ClassSetupParameter):
%
% outputPath - Path to the folder where the test results are stored.
%
% srsChEstimatorUnittest Properties (TestParameter):
%
% configuration - Description of the allocated REs and DM-RS pattern.
% SubcarrierSpacing - Subcarrier spacing in kHz.
% FrequencyHopping - Frequency hopping type.
% CarrierOffset - Carrier frequency offset, as a fraction of the subcarrier spacing.
%
% srsChEstimatorUnittest Methods:
%
% characterize - Draws the empircical MSE performance curve of the estimator.
%
% srsChEstimatorUnittest Methods (TestTags = {'testvector'}):
%
% testvectorGenerationCases - Generates a test vector according to the provided
% parameters.
%
% srsChEstimatorUnittest Methods (TestTags = {'testmex'}):
%
% compareMex - Compares mex results with those from the reference estimator.
%
% srsChEstimatorUnittest Methods (Access = protected):
%
% addTestIncludesToHeaderFile - Adds include directives to the test header file.
% addTestDefinitionToHeaderFile - Adds details (e.g., type/variable declarations)
% to the test header file.
%
% See also matlab.unittest.
% Copyright 2021-2024 Software Radio Systems Limited
%
% This file is part of srsRAN-matlab.
%
% srsRAN-matlab is free software: you can redistribute it and/or
% modify it under the terms of the BSD 2-Clause License.
%
% srsRAN-matlab is distributed in the hope that it will be useful,
% but WITHOUT ANY WARRANTY; without even the implied warranty of
% MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
% BSD 2-Clause License for more details.
%
% A copy of the BSD 2-Clause License can be found in the LICENSE
% file in the top-level directory of this distribution.
classdef srsChEstimatorUnittest < srsTest.srsBlockUnittest
properties (Constant)
%Name of the tested block.
srsBlock = 'port_channel_estimator'
%Type of the tested block, including layers.
srsBlockType = 'phy/upper/signal_processors'
end % of properties (Constant)
properties (Hidden, Constant)
% Number of resource elements in a RB and OFDM symbols in a slot.
NRE = 12
nSymbolsSlot = 14
end % of properties (Hidden, Constant)
properties (Hidden, SetAccess=private)
% Fix BWP size and start as well as the frame number, since they
% are irrelevant for the test.
NSizeBWP = 51
NStartBWP = 1
NSizeGrid = 52 % srsChEstimatorUnittest.NSizeBWP + srsChEstimatorUnittest.NStartBWP
end % of properties (Hidden, SetAccess=private)
properties (ClassSetupParameter)
%Path to results folder (old 'port_channel_estimator' tests will be erased).
outputPath = {['testChEstimator', char(datetime('now', 'Format', 'yyyyMMdd''T''HHmmss'))]}
end
properties (TestParameter)
%Configuration.
% A configuration structure array with fields:
% nPRBs - Number of allocated PRBs (0...51)
% symbolAllocation - A two-element array denoting the first allocated OFDM symbol (0...13)
% and the number of allocated OFDM symbols (1...14).
% dmrsOffset - Number of non-DM-RS REs at the beginning of the RB (0, 1).
% dmrsStrideSCS - DM-RS frequency domain stride (1, 2, 3), that is the distance
% between two consecutive DM-RS REs (distance of 1 being back-to-back).
% dmrsStrideTime - Stride between OFDM symbols containing DM-RS (1, 2, 4, 6, 20).
% Use 20 for a single DM-RS symbol.
% betaDMRS - The gain of the DM-RS pilots with respect to the data
% symbols in dB (0, 3).
% smoothing - The frequency-domain smoothing strategy to be used with the
% current configuration ('filter', 'mean', 'none').
% cfocompensate - A boolean flag denoting whether the channel estimator should
% compensate (true) or not (false) the CFO.
configuration = {...
struct(... % #1: PUSCH DM-RS configuration Type 1 (inspired to).
'nPRBs', 3, ...
'symbolAllocation', [0, 14], ...
'dmrsOffset', 0, ...
'dmrsStrideSCS', 2, ...
'dmrsStrideTime', 4, ...
'betaDMRS', -3, ...
'smoothing', 'filter', ...
'cfocompensate', true ...
),...
struct(... % #2: PUSCH DM-RS configuration Type 1 (inspired to).
'nPRBs', 20, ...
'symbolAllocation', [0, 14], ...
'dmrsOffset', 0, ...
'dmrsStrideSCS', 2, ...
'dmrsStrideTime', 4, ...
'betaDMRS', -3, ...
'smoothing', 'filter', ...
'cfocompensate', true ...
), ...
struct(... % #3: PUSCH DM-RS configuration Type 1 (inspired to).
'nPRBs', 51, ...
'symbolAllocation', [0, 14], ...
'dmrsOffset', 0, ...
'dmrsStrideSCS', 2, ...
'dmrsStrideTime', 4, ...
'betaDMRS', -3, ...
'smoothing', 'filter', ...
'cfocompensate', true ...
), ...
struct(... % #4: PUCCH Format 1 (inspired to).
'nPRBs', 1, ...
'symbolAllocation', [8, 4], ...
'dmrsOffset', 0, ...
'dmrsStrideSCS', 1, ...
'dmrsStrideTime', 2, ...
'betaDMRS', 0, ...
'smoothing', 'mean', ...
'cfocompensate', false ...
), ...
struct(... % #5: PUCCH Format 1 (inspired to).
'nPRBs', 1, ...
'symbolAllocation', [0, 14], ...
'dmrsOffset', 0, ...
'dmrsStrideSCS', 1, ...
'dmrsStrideTime', 2, ...
'betaDMRS', 0, ...
'smoothing', 'mean', ...
'cfocompensate', false ...
), ...
struct(... % #6: PUCCH Format 2 (inspired to).
'nPRBs', 1, ...
'symbolAllocation', [0, 2], ...
'dmrsOffset', 1, ...
'dmrsStrideSCS', 3, ...
'dmrsStrideTime', 1, ...
'betaDMRS', 0, ...
'smoothing', 'filter', ...
'cfocompensate', true ...
), ...
struct(... % #7: PUCCH Format 2 (inspired to).
'nPRBs', 6, ...
'symbolAllocation', [5, 1], ...
'dmrsOffset', 1, ...
'dmrsStrideSCS', 3, ...
'dmrsStrideTime', 1, ...
'betaDMRS', 0, ...
'smoothing', 'filter', ...
'cfocompensate', true ...
), ...
struct(... % #8: PUCCH Format 2 (inspired to).
'nPRBs', 16, ...
'symbolAllocation', [5, 2], ...
'dmrsOffset', 1, ...
'dmrsStrideSCS', 3, ...
'dmrsStrideTime', 1, ...
'betaDMRS', 0, ...
'smoothing', 'filter', ...
'cfocompensate', true ...
), ...
}
%Subcarrier spacing in kHz.
SubcarrierSpacing = {15, 30}
%Frequency hopping type ('neither', 'intraSlot').
% Note: Interslot frequency hopping is currently not considered.
FrequencyHopping = {'neither', 'intraSlot'}
%Carrier frequency offset, as a fraction of the subcarrier spacing.
CarrierOffset = {0, 0.007, -0.013, 0.027}
end % of properties (TestParameter)
properties (Hidden)
%OFDM symbol in which the second hop starts (if any).
secondHop
%Mask of OFDM symbols carrying DM-RS.
DMRSsymbols
%Mask of REs carrying DM-RS (relative to one PRB and one OFDM symbol).
DMRSREmask
end % of properties (Hidden)
methods (Access = protected)
function addTestIncludesToHeaderFile(~, fileID)
%addTestIncludesToHeaderFile(OBJ, FILEID) adds include directives to
% the header file pointed by FILEID, which describes the test vectors.
fprintf(fileID, '#include "../../support/resource_grid_test_doubles.h"\n');
fprintf(fileID, '#include "srsran/phy/upper/signal_processors/port_channel_estimator.h"\n');
fprintf(fileID, '#include "srsran/phy/upper/signal_processors/port_channel_estimator_parameters.h"\n');
fprintf(fileID, '#include "srsran/support/file_vector.h"\n');
fprintf(fileID, '#include <optional>\n');
end
function addTestDefinitionToHeaderFile(~, fileID)
%addTestDefinitionToHeaderFile(OBJ, FILEID) adds test details (e.g., type
% and variable declarations) to the header file pointed by FILEID, which
% describes the test vectors.
fprintf(fileID, 'struct test_case_t {\n');
fprintf(fileID, ' port_channel_estimator::configuration cfg;\n');
fprintf(fileID, ' port_channel_estimator_fd_smoothing_strategy smoothing;\n');
fprintf(fileID, ' bool compensate_cfo = false;\n');
fprintf(fileID, ' unsigned grid_size_prbs = 0;\n');
fprintf(fileID, ' float rsrp = 0;\n');
fprintf(fileID, ' float epre = 0;\n');
fprintf(fileID, ' float snr_true = 0;\n');
fprintf(fileID, ' float snr_est = 0;\n');
fprintf(fileID, ' float noise_var_est = 0;\n');
fprintf(fileID, ' float ta_us = 0;\n');
fprintf(fileID, ' float cfo_true_Hz = 0;\n');
fprintf(fileID, ' std::optional<float> cfo_est_Hz = 0;\n');
fprintf(fileID, ' file_vector<resource_grid_reader_spy::expected_entry_t> grid;\n');
fprintf(fileID, ' file_vector<cf_t> pilots;\n');
fprintf(fileID, ' file_vector<resource_grid_reader_spy::expected_entry_t> estimates;\n');
fprintf(fileID, '};\n');
end
end % of methods (Access = protected)
methods (Test, TestTags = {'testvector'})
function testvectorGenerationCases(obj, configuration, SubcarrierSpacing, ...
FrequencyHopping, CarrierOffset)
%testvectorGenerationCases - Generates a test vector according to the provided
% CONFIGURATION, SUBCARRIERSPACING, FREQUENCYHOPPING type and CARRIEROFFSET.
import srsLib.phy.upper.signal_processors.srsChannelEstimator
import srsLib.ran.utils.scs2cps
import srsTest.helpers.approxbf16
import srsTest.helpers.writeResourceGridEntryFile
import srsTest.helpers.writeComplexFloatFile
obj.assumeFalse(((configuration.nPRBs == obj.NSizeBWP) || (configuration.symbolAllocation(2) == 1)) ...
&& strcmp(FrequencyHopping, 'intraSlot'), ...
'Cannot do frequency hopping if the entire BWP is allocated or if using a single OFDM symbol.');
assert((sum(configuration.symbolAllocation) <= obj.nSymbolsSlot), ...
'srsran_matlab:srsChEstimatorUnittest', 'Time allocation exceeds slot length.');
% Generate a unique test ID.
testID = obj.generateTestID;
% Configure each hop.
[hop1, hop2] = obj.configureHops(configuration, FrequencyHopping);
% Build DM-RS-like pilots.
nDMRSsymbols = sum(obj.DMRSsymbols);
nPilots = configuration.nPRBs * sum(obj.DMRSREmask) * nDMRSsymbols;
pilots = (2 * randi([0 1], nPilots, 2) - 1) * [1; 1j] / sqrt(2);
pilots = reshape(pilots, [], nDMRSsymbols);
betaDMRS = 10^(-configuration.betaDMRS / 20);
% Place pilots on the resource grid.
transmittedRG = obj.transmitPilots(pilots, betaDMRS, hop1, hop2);
% For now, consider a single-tap channel (max delay is 1/4 of
% the cyclic prefix length).
fftSize = obj.NSizeGrid * obj.NRE;
channelDelay = randi([0, floor(fftSize * 0.07 * 0.25)]);
channelCoef = exp(2j * pi * rand);
channelTF = fft([zeros(channelDelay, 1); channelCoef; zeros(5, 1)], fftSize);
channelTF = fftshift(channelTF);
% We assume the channel constant over the entire slot...
channelRG = repmat(channelTF, 1, obj.nSymbolsSlot);
% ... but for CFO.
cfo = CarrierOffset; % Fraction of the SCS.
CPDurations = scs2cps(SubcarrierSpacing);
if cfo ~= 0
cfoVal = CPDurations * SubcarrierSpacing;
cfoVal(2:end) = cfoVal(2:end) + 1;
cfoVal = cumsum(cfoVal) * cfo;
cfoVal = exp(2j * pi * cfoVal);
channelRG = (channelRG .* cfoVal) * exp(1j * pi * ((fftSize - 1) / fftSize) * cfo);
end
% Compute received resource grid.
receivedRG = channelRG .* transmittedRG;
SNR = 20; % dB
noiseVar = 10^(-SNR/10);
noise = randn(size(receivedRG)) + 1j * randn(size(receivedRG));
noise(receivedRG == 0) = 0;
noise = noise * sqrt(noiseVar / 2);
receivedRG = receivedRG + noise;
EstimatorConfig.DMRSSymbolMask = obj.DMRSsymbols;
EstimatorConfig.DMRSREmask = obj.DMRSREmask;
EstimatorConfig.scs = SubcarrierSpacing * 1000;
EstimatorConfig.CyclicPrefixDurations = CPDurations;
EstimatorConfig.Smoothing = configuration.smoothing;
EstimatorConfig.CFOCompensate = configuration.cfocompensate;
[channelEst, noiseEst, rsrp, epre, timeAlignment, cfoEst] = srsChannelEstimator(approxbf16(receivedRG), ...
pilots, betaDMRS, hop1, hop2, EstimatorConfig);
% TODO: The ratio of the two quantities below should give a metric that allows us
% to decide whether pilots were sent or not. However, it should be normalized
% and it's a bit tricky.
% detectMetricNum = detectMetricNum / nDMRSsymbols;
% detectMetricDen = noiseEst;
% detectionMetric = detectMetricNum / detectMetricDen;
snrEst = rsrp / betaDMRS^2 / noiseEst;
% A few very loose checks, just to ensure we are not completely out of place.
if (configuration.nPRBs > 2)
chEstIdx = (channelEst ~= 0);
obj.assertEqual(channelEst(chEstIdx), channelRG(chEstIdx), "Wrong channel coefficients.", RelTol = 0.4);
obj.assertEqual(noiseEst, noiseVar, "Wrong noise variance.", RelTol = 0.8);
obj.assertEqual(snrEst, 10^(SNR/10), "Wrong SNR.", RelTol = 2.5);
obj.assertEqual(timeAlignment, channelDelay / fftSize / SubcarrierSpacing / 1000, ...
"Wrong time alignment.", AbsTol = 2e-7);
cfoHz = cfo * SubcarrierSpacing * 1000;
if (~isempty(cfoEst) && (abs(cfoEst - cfoHz) > 40) && ((cfoHz == 0) || abs(cfoEst / cfoHz - 1) > 0.7))
warning('srsran_matlab:srsChEstimatorUnittest', 'Estimated CFO = %f, True CFO = %f.', cfoEst, cfoHz);
end
end
% Write the received resource grid.
[scs, syms, vals] = find(receivedRG);
obj.saveDataFile('_test_input_rg', testID, @writeResourceGridEntryFile, ...
vals, [scs, syms, zeros(length(scs), 1)] - 1);
% Write the estimated channel.
[scs, syms, vals] = find(channelEst);
obj.saveDataFile('_test_output_ch_est', testID, @writeResourceGridEntryFile, ...
vals, [scs, syms, zeros(length(scs), 1)] - 1);
% Write the pilots.
obj.saveDataFile('_test_pilots', testID, @writeComplexFloatFile, pilots(:));
dmrsPattern = {...
obj.DMRSsymbols, ... % symbols
hop1.maskPRBs, ... % rb_mask
hop2.maskPRBs, ... % rb_mask2
obj.secondHop, ... % hopping_symbol_index
obj.DMRSREmask, ... % re_pattern
};
startSymbol = configuration.symbolAllocation(1);
nAllocatedSymbols = configuration.symbolAllocation(2);
scsString = sprintf('subcarrier_spacing::kHz%d', SubcarrierSpacing);
configurationOut = {...
scsString, ... % scs
'cyclic_prefix::NORMAL', ... % cp
startSymbol, ... % first_symbol
nAllocatedSymbols, ... % nof_symbols
{dmrsPattern}, ... % dmrs_patterns
{0}, ... % rx_ports
betaDMRS, ... % betaDMRS
};
if isempty(cfoEst)
cfoEst = {};
end
smoothingOut = ['port_channel_estimator_fd_smoothing_strategy::' configuration.smoothing];
context = {...
configurationOut, ...
smoothingOut, ...
configuration.cfocompensate, ...
obj.NSizeGrid, ...
rsrp, ...
epre, ...
SNR, ...
10 * log10(snrEst), ...
noiseEst, ...
timeAlignment * 1e6, ...
cfo * SubcarrierSpacing * 1000, ...
cfoEst, ...
};
testCaseString = obj.testCaseToString(testID, context, false, ...
'_test_input_rg', '_test_pilots', '_test_output_ch_est');
% Add the test to the header file.
obj.addTestToHeaderFile(obj.headerFileID, testCaseString);
end % of function testvectorGenerationCases(...)
end % of methods (Test, TestTags = {'testvector'})
methods (Test, TestTags = {'testmex'})
function compareMex(obj, configuration, SubcarrierSpacing, FrequencyHopping, CarrierOffset)
%compareMex - Compare mex results with those from the reference estimator for
% a given CONFIGURATION, SUBCARRIERSPACING, FREQUENCYHOPPING type and CARRIEROFFSET.
import srsLib.phy.upper.signal_processors.srsChannelEstimator
import srsLib.ran.utils.scs2cps
import srsMEX.phy.srsMultiPortChannelEstimator
import srsTest.helpers.approxbf16
obj.assumeFalse(((configuration.nPRBs == obj.NSizeBWP) || (configuration.symbolAllocation(2) == 1)) ...
&& strcmp(FrequencyHopping, 'intraSlot'), ...
'Cannot do frequency hopping if the entire BWP is allocated or if using a single OFDM symbol.');
assert((sum(configuration.symbolAllocation) <= obj.nSymbolsSlot), ...
'srsran_matlab:srsChEstimatorUnittest', 'Time allocation exceeds slot length.');
% Configure each hop.
[hop1, hop2] = obj.configureHops(configuration, FrequencyHopping);
% Build DM-RS-like pilots.
nDMRSsymbols = sum(obj.DMRSsymbols);
nPilots = configuration.nPRBs * sum(obj.DMRSREmask) * nDMRSsymbols;
pilots = (2 * randi([0 1], nPilots, 2) - 1) * [1; 1j] / sqrt(2);
pilots = reshape(pilots, [], nDMRSsymbols);
betaDMRS = 10^(-configuration.betaDMRS / 20);
% Place pilots on the resource grid.
transmittedRG = obj.transmitPilots(pilots, betaDMRS, hop1, hop2);
% For now, consider a single-tap channel (max delay is 1/4 of
% the cyclic prefix length).
fftSize = obj.NSizeGrid * obj.NRE;
channelDelay = randi([0, floor(fftSize * 0.07 * 0.25)]);
channelCoef = exp(2j * pi * rand);
channelTF = fft([zeros(channelDelay, 1); channelCoef; zeros(5, 1)], fftSize);
channelTF = fftshift(channelTF);
% We assume the channel constant over the entire slot...
channelRG = repmat(channelTF, 1, obj.nSymbolsSlot);
% ... but for CFO.
cfo = CarrierOffset; % Fraction of the SCS.
CPDurations = scs2cps(SubcarrierSpacing);
if cfo ~= 0
cfoVal = CPDurations * SubcarrierSpacing;
cfoVal(2:end) = cfoVal(2:end) + 1;
cfoVal = cumsum(cfoVal) * cfo;
cfoVal = exp(2j * pi * cfoVal);
channelRG = (channelRG .* cfoVal) * exp(1j * pi * ((fftSize - 1) / fftSize) * cfo);
end
% Compute received resource grid.
receivedRG = channelRG .* transmittedRG;
SNR = 20; % dB
noiseVar = 10^(-SNR/10);
noise = randn(size(receivedRG)) + 1j * randn(size(receivedRG));
noise(receivedRG == 0) = 0;
noise = noise * sqrt(noiseVar / 2);
receivedRG = receivedRG + noise;
EstimatorConfig.DMRSSymbolMask = obj.DMRSsymbols;
EstimatorConfig.DMRSREmask = obj.DMRSREmask;
EstimatorConfig.scs = 15000;
EstimatorConfig.CyclicPrefixDurations = CPDurations;
EstimatorConfig.Smoothing = configuration.smoothing;
EstimatorConfig.CFOCompensate = configuration.cfocompensate;
[channelEst, noiseEst, rsrp, epre, timeAlignment, cfoEst] = srsChannelEstimator(approxbf16(receivedRG), ...
pilots, betaDMRS, hop1, hop2, EstimatorConfig);
% Cast input for the mex estimator.
pilotRBMask = hop1.maskPRBs * hop1.DMRSsymbols';
if (~isempty(hop2.maskPRBs) && ~isempty(hop2.DMRSsymbols))
pilotRBMask = pilotRBMask + hop2.maskPRBs * hop2.DMRSsymbols';
end
pilotMask = kron(pilotRBMask, hop1.DMRSREmask);
pilotIndices = find(pilotMask);
mexEstimator = srsMultiPortChannelEstimator(Smoothing = configuration.smoothing, CompensateCFO = configuration.cfocompensate);
[channelEstMEX, noiseEstMEX, extra] ...
= mexEstimator(receivedRG, configuration.symbolAllocation, pilotIndices, ...
pilots(:), HoppingIndex = hop2.startSymbol, BetaScaling = betaDMRS); %#ok<FNDSB>
toleranceTA = 1000 / (4096 * SubcarrierSpacing);
chEstIdx = (channelEst ~= 0);
obj.assertEqual(channelEstMEX(chEstIdx), channelEst(chEstIdx), 'Wrong channel estimates.', AbsTol = 0.008);
obj.assertEqual(noiseEstMEX, noiseEst, 'Wrong noise variance estimate.', AbsTol = 5e-4);
obj.assertEqual(extra.RSRP, rsrp, 'Wrong RSRP estimate.', AbsTol = 5e-4);
obj.assertEqual(extra.EPRE, epre, 'Wrong EPRE estimate.', AbsTol = 5e-4);
obj.assertEqual(extra.SINR, rsrp / betaDMRS^2 / noiseEst, 'Wrong SINR estimate.', RelTol = 0.004);
obj.assertEqual(extra.TimeAlignment, timeAlignment, 'Wrong time alignment estimate.', RelTol = toleranceTA);
obj.assertEqual(extra.CFO, cfoEst, 'Wrong CFO.', RelTol = 0.04);
end % of function compareMex(...)
end % of methods (Test, TestTags = {'testmex'})
methods % public
function [mse, noiseEst, rsrpEst, epreEst, cfoEst, crlb] = characterize(obj, configuration, ...
FrequencyHopping, scs, channelType, delay, doppler, cfo, snrValues, nRuns, sizeBWP)
%characterize - Draw the empirical MSE performance curve of the estimator.
% MSE = characterize(OBJ, CONFIGURATION, FREQUENCYHOPPING, SCS, CHANNELTYPE, DELAY, DOPPLER, CFO, SNRVALUES, NRUNS)
% returns the empirical mean squared error of the channel estimation after NRUNS simulations
% and for all SNRVALUES. CONFIGURATION, FREQUENCYHOPPING and SCS provide the physical
% channel configuration and CHANNELTYPE, DELAY, DOPPLER and CFO specify the simulated channel model.
% Note: DELAY is the delay spread for the IEEE channel types, and the Path delay
% for the 'pure-delay' channel type.
% Note: DOPPLER is the maximum Doppler shift in hertz (effect of scattering), not to
% be confused with the CFO.
%
% MSE = characterize(..., BWP) also changes the BWP size (expressed as a number of RBs).
% The default BWP size is 51.
%
% [MSE, NOISEEST, RSRPEST, EPREEST, CFOEST, CRLB] = characterize(...) also returns the
% estimates of noise variance, RSRP, EPRE and CFO for all runs and all SNR values,
% as well as the CRLB for the channel estimation. The CRLB is computed assuming
% the entire band is available for estimation, with pilots positioned with
% the same pattern as the DM-RS (first column) or with pilots in all REs
% (second column).
%
% For CONFIGURATION and FREQUENCYHOPPING, see <a href="matlab:help srsChEstimatorUnittest">the main class documentation</a>.
% SNRVALUES is an array of SNR values in decibel.
% NRUNS is an integer number of simulations.
arguments
obj (1, 1) srsChEstimatorUnittest
configuration (1, 1) struct {mustBeConfiguration}
FrequencyHopping (1, :) char {mustBeMember(FrequencyHopping, {'neither', 'intraSlot'})}
scs (1, 1) double {mustBeMember(scs, [15, 30])}
channelType (1, :) char {mustBeMember(channelType, {'pure-delay', ...
'TDL-A', 'TDL-B', 'TDL-C', 'TDL-D', 'TDL-E', ...
'TDLA30', 'TDLB100', 'TDLC300', 'TDLC60'})}
delay (1, 1) double {mustBeReal, mustBeNonnegative}
doppler (1, 1) double {mustBeReal, mustBeNonnegative}
cfo (1, 1) double {mustBeReal}
snrValues double {mustBeReal, mustBeVector}
nRuns (1, 1) double {mustBeNonnegative, mustBeInteger}
sizeBWP (1, 1) double = NaN
end
import srsLib.phy.upper.signal_processors.srsChannelEstimator
if ~isempty(delay)
validateattributes(delay, 'double', {'nonnegative'});
end
if ~isnan(sizeBWP)
validateattributes(sizeBWP, 'double', {'positive', 'integer', '<=', 273});
obj.NSizeBWP = sizeBWP;
obj.NSizeGrid = obj.NStartBWP + obj.NSizeBWP;
end
% Cannot do frequency hopping if the entire BWP is allocated or if using a single OFDM symbol.
assert(~(((configuration.nPRBs == obj.NSizeBWP) || (configuration.symbolAllocation(2) == 1)) ...
&& strcmp(FrequencyHopping, 'intraSlot')), 'srsgnb_matlab:srsChEstimatorUnittest', ...
'Unfeasible configuration-frequency hopping combination.');
assert((sum(configuration.symbolAllocation) <= obj.nSymbolsSlot), ...
'srsgnb_matlab:srsChEstimatorUnittest', 'Time allocation exceeds slot length.');
% Configure carrier.
carrier = nrCarrierConfig;
carrier.CyclicPrefix = 'Normal';
carrier.SubcarrierSpacing = scs; % kHz
carrier.NSlot = 0;
carrier.NSizeGrid = obj.NSizeGrid;
waveformInfo = nrOFDMInfo(carrier);
channel = configureChannel(channelType, delay, doppler, waveformInfo.SampleRate, ...
carrier.SubcarrierSpacing);
% Configure each hop.
[hop1, hop2] = obj.configureHops(configuration, FrequencyHopping);
% Build DM-RS-like pilots.
nDMRSsymbols = sum(obj.DMRSsymbols);
nPilots = configuration.nPRBs * sum(obj.DMRSREmask) * nDMRSsymbols;
pilots = (2 * randi([0 1], nPilots, 2) - 1) * [1; 1j] / sqrt(2);
pilots = reshape(pilots, [], nDMRSsymbols);
betaDMRS = 10^(-configuration.betaDMRS / 20);
% Place pilots on the resource grid.
transmittedRG = obj.transmitPilots(pilots, betaDMRS, hop1, hop2);
transmittedWF = nrOFDMModulate(carrier, transmittedRG);
nEstSCS = hop1.nPRBs * obj.NRE;
if ~isempty(hop2.maskPRBs)
nEstSCS = nEstSCS * 2;
end
mse = zeros(length(snrValues), nEstSCS);
noiseEst = zeros(length(snrValues), nRuns);
rsrpEst = zeros(length(snrValues), nRuns);
epreEst = zeros(length(snrValues), nRuns);
cfoEst = zeros(length(snrValues), nRuns);
CPDurations = waveformInfo.CyclicPrefixLengths(1:14);
CPDurations = CPDurations / sum(CPDurations) / scs;
% Configure estimator.
EstimatorConfig.DMRSSymbolMask = obj.DMRSsymbols;
EstimatorConfig.DMRSREmask = obj.DMRSREmask;
EstimatorConfig.nPilotsNoiseAvg = sum(obj.DMRSREmask);
EstimatorConfig.scs = scs * 1000; % SCS in hertz
EstimatorConfig.CyclicPrefixDurations = CPDurations;
EstimatorConfig.Smoothing = configuration.smoothing;
EstimatorConfig.CFOCompensate = configuration.cfocompensate;
for iRun = 1:nRuns
reset(channel);
[receivedWF0, pathGains, sampleTimes] = channel(transmittedWF);
if cfo ~= 0
nSamples = size(receivedWF0, 1);
if (~exist('cfoPhase', 'var') || length(cfoPhase) ~= nSamples)
timeIx = (0:length(receivedWF0)-1).';
cfoPhase = exp(2j * pi * timeIx * cfo / waveformInfo.SampleRate);
end
receivedWF0 = receivedWF0 .* cfoPhase;
end
noise0 = randn(size(receivedWF0)) + 1j * randn(size(receivedWF0));
iSNR = 0;
for SNR = snrValues
iSNR = iSNR + 1;
noiseVar = 10^(-SNR/10) / waveformInfo.Nfft;
noise = noise0 * sqrt(noiseVar / 2);
receivedWF = receivedWF0 + noise;
% Compute received resource grid.
receivedRG = nrOFDMDemodulate(carrier, receivedWF);
[channelEst, noiseEstL, rsrpEstL, epreEstL, ~, cfoEstL] ...
= srsChannelEstimator(receivedRG, pilots, betaDMRS, hop1, hop2, EstimatorConfig);
noiseEst(iSNR, iRun) = noiseEstL;
rsrpEst(iSNR, iRun) = rsrpEstL;
epreEst(iSNR, iRun) = epreEstL;
cfoEst(iSNR, iRun) = cfoEstL;
% Get the true channel, for comparison.
pathFilters = channel.getPathFilters();
channelTrue = nrPerfectChannelEstimate(carrier, pathGains, pathFilters, 0, sampleTimes);
if cfo ~= 0
cfoNorm = cfo / scs / 1000;
cfoFreq = [waveformInfo.CyclicPrefixLengths(1) waveformInfo.CyclicPrefixLengths(2:14) + waveformInfo.Nfft];
cfoFreq = cumsum(cfoFreq) * cfoNorm / waveformInfo.Nfft;
cfoFreq = exp(2j * pi * cfoFreq);
channelTrue = channelTrue * diag(cfoFreq) * exp(1j * pi * ((waveformInfo.Nfft - 1) / waveformInfo.Nfft) * cfoNorm);
end
% Just for debugging/analysis purposes: set to true to visualize
% the effect of channel and channel estimation on a random QAM
% points.
if false
whatSymbol = 1+hop1.startSymbol; %#ok<UNRCH>
whatSCS = (channelEst(:, whatSymbol) ~= 0);
nSCS = sum(whatSCS);
% Create some random QAM points.
fakeSymbols = srsTest.helpers.randmod('QPSK', [nSCS, 50]);
% Apply the true channel and ZF-equalize with the estimated channel (SC-wise).
rr = diag(channelTrue(whatSCS, whatSymbol) ./ channelEst(whatSCS, whatSymbol)) * fakeSymbols;
if (size(rr, 1) >= 60)
% Split edge and middle points, to visualize the difference in
% the estimation performance.
rrEdge = rr([1:24, end-23:end], :);
rrMiddle = rr(25:end-24, :);
plot(real(rrEdge(:)), imag(rrEdge(:)), 'rx', real(rrMiddle(:)), imag(rrMiddle(:)), 'bx')
else
plot(real(rr(:)), imag(rr(:)), 'bx')
end
pause
end
scsIdx = obj.NRE * hop1.PRBstart + (1: obj.NRE * hop1.nPRBs);
estErrors = channelEst(scsIdx, hop1.CHsymbols) - channelTrue(scsIdx, hop1.CHsymbols);
SQestErrors = sum(abs(estErrors).^2, 2);
if ~isempty(hop2.maskPRBs)
scsIdx = obj.NRE * hop2.PRBstart + (1: obj.NRE * hop2.nPRBs);
estErrors2 = channelEst(scsIdx, hop2.CHsymbols) - channelTrue(scsIdx, hop2.CHsymbols);
SQestErrors2 = sum(abs(estErrors2).^2, 2);
else
SQestErrors2 = [];
end
mse(iSNR, :) = mse(iSNR, :) + [SQestErrors; SQestErrors2]' / nRuns;
end
end
crlb = repmat(10.^(-snrValues(:)/10), 1, 2) / betaDMRS^2 / sum(hop1.DMRSsymbols);
crlb = (crlb' .* computeCRLB(hop1.maskPRBs, hop1.DMRSREmask))';
end % of function characterize(...)
end % of methods % public
methods (Access = private)
function [hop1, hop2] = configureHops(obj, configuration, FrequencyHopping)
%Creates a description of the resources allocated in each hop.
startSymbol = configuration.symbolAllocation(1);
nAllocatedSymbols = configuration.symbolAllocation(2);
dmrsStrideTime = configuration.dmrsStrideTime;
% Create a mask of the OFDM symbols carrying DM-RS.
obj.DMRSsymbols = false(14, 1);
obj.DMRSsymbols(startSymbol + (1:dmrsStrideTime:nAllocatedSymbols)) = true;
nPRBs = configuration.nPRBs;
dmrsOffset = configuration.dmrsOffset;
dmrsStrideSCS = configuration.dmrsStrideSCS;
% Create a DM-RS pattern from the offset and stride.
obj.DMRSREmask = false(obj.NRE, 1);
obj.DMRSREmask((dmrsOffset + 1):dmrsStrideSCS:end) = true;
if strcmp(FrequencyHopping, 'intraSlot')
PRBstart = randperm(obj.NSizeBWP - nPRBs + 1, 2) - 1 + obj.NStartBWP;
obj.secondHop = startSymbol + floor(nAllocatedSymbols / 2);
hopMask = [true(obj.secondHop, 1); false(obj.nSymbolsSlot - obj.secondHop, 1)];
hop1.DMRSsymbols = (obj.DMRSsymbols & hopMask);
hop1.DMRSREmask = obj.DMRSREmask;
hop1.PRBstart = PRBstart(1);
hop1.nPRBs = nPRBs;
hop1.maskPRBs = false(obj.NSizeGrid, 1);
hop1.maskPRBs(hop1.PRBstart + (1:nPRBs)) = true;
hop1.startSymbol = startSymbol;
hop1.nAllocatedSymbols = floor(nAllocatedSymbols / 2);
hop1.CHsymbols = false(obj.nSymbolsSlot, 1);
hop1.CHsymbols(hop1.startSymbol + (1:hop1.nAllocatedSymbols)) = true;
hop2.DMRSsymbols = (obj.DMRSsymbols & (~hopMask));
hop2.DMRSREmask = obj.DMRSREmask;
hop2.PRBstart = PRBstart(2);
hop2.nPRBs = nPRBs;
hop2.maskPRBs = false(obj.NSizeGrid, 1);
hop2.maskPRBs(hop2.PRBstart + (1:nPRBs)) = true;
hop2.startSymbol = obj.secondHop;
hop2.nAllocatedSymbols = ceil(nAllocatedSymbols / 2);
hop2.CHsymbols = false(obj.nSymbolsSlot, 1);
hop2.CHsymbols(hop2.startSymbol + (1:hop2.nAllocatedSymbols)) = true;
else
PRBstart = randi([0, obj.NSizeBWP - nPRBs]) + obj.NStartBWP;
obj.secondHop = 'std::nullopt';
hop1.DMRSsymbols = obj.DMRSsymbols;
hop1.DMRSREmask = obj.DMRSREmask;
hop1.PRBstart = PRBstart;
hop1.nPRBs = nPRBs;
hop1.maskPRBs = false(obj.NSizeGrid, 1);
hop1.maskPRBs(hop1.PRBstart + (1:nPRBs)) = true;
hop1.startSymbol = startSymbol;
hop1.nAllocatedSymbols = nAllocatedSymbols;
hop1.CHsymbols = false(obj.nSymbolsSlot, 1);
hop1.CHsymbols(hop1.startSymbol + (1:hop1.nAllocatedSymbols)) = true;
hop2.DMRSsymbols = [];
hop2.maskPRBs = {};
hop2.startSymbol = [];
end
end % of function [hop1 hop2] = configureHops()
function transmittedRG = transmitPilots(obj, pilots, betaDMRS, hop1, hop2)
%Places the pilots on the correct REs and with the correct power on the resource grid.
transmittedRG = zeros(obj.NSizeGrid * obj.NRE, obj.nSymbolsSlot);
nPilotSymbolsHop1 = sum(hop1.DMRSsymbols);
processHop(hop1, pilots(:, 1:nPilotSymbolsHop1));
if ~isempty(hop2.DMRSsymbols)
processHop(hop2, pilots(:, (nPilotSymbolsHop1 + 1):end));
end
% Nested functions
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
function processHop(hop_, pilots_)
%Processes the DM-RS corresponding to a single hop.
% Create a mask for all subcarriers carrying DM-RS.
maskPRBs_ = hop_.maskPRBs;
maskREs_ = (kron(maskPRBs_, obj.DMRSREmask) > 0);
transmittedRG(maskREs_, hop_.DMRSsymbols) = betaDMRS * pilots_;
end % of function processHop(hop_, pilots_)
end % of function transmittedRG = transmitPilots(pilots, hop1, hop2)
end % of methods (Access = private)
end % of classdef srsChEstimatorUnittest
function channel = configureChannel(chModel, delay, doppler, SampleRate, SubcarrierSpacing)
channel = nrTDLChannel;
channel.NumTransmitAntennas = 1;
channel.NumReceiveAntennas = 1;
channel.MaximumDopplerShift = doppler;
channel.SampleRate = SampleRate;
channel.RandomStream = 'Global stream';
if strcmp(chModel, 'pure-delay')
channel.DelayProfile = 'Custom';
if isempty(delay)
% Random delay, at most one fourth of the cyclic prefix length.
channel.PathDelays = rand() * 0.018 / SubcarrierSpacing / 1000;
else
channel.PathDelays = delay;
end
channel.AveragePathGains = 0;
channel.FadingDistribution = 'Rayleigh';
elseif ismember(chModel, {'TDL-A', 'TDL-B', 'TDL-C', 'TDL-D', 'TDL-E'})
channel.DelayProfile = chModel;
if ~isempty(delay)
channel.DelaySpread = delay;
end
elseif ismember(chModel, {'TDLA30', 'TDLB100', 'TDLC300', 'TDLC60'})
channel.DelayProfile = chModel;
else
error('srsgnb_matlab:srsChEstimatorUnittest:configureChannel', ...
'Unknown channel model %s', chModel);
end
end
function mustBeConfiguration(a)
if ~isfield(a, 'nPRBs')
eidType = 'srsChEstimatorUnittest:characterize';
msgType = 'Missing configuration field "nPRBs."';
throwAsCaller(MException(eidType, msgType));
end
mustBeScalarOrEmpty(a.nPRBs);
mustBeInteger(a.nPRBs);
mustBeInRange(a.nPRBs, 1, 273);
if ~isfield(a, 'symbolAllocation')
eidType = 'srsChEstimatorUnittest:characterize';
msgType = 'Missing configuration field "symbolAllocation".';
throwAsCaller(MException(eidType, msgType));
end
mustBeVector(a.symbolAllocation)
if numel(a.symbolAllocation) ~= 2
eidType = 'srsChEstimatorUnittest:characterize';
msgType = 'Configuration field "symbolAllocation" should be an array of two elements.';
throwAsCaller(MException(eidType, msgType));
end
mustBeInteger(a.symbolAllocation);
mustBeNonnegative(a.symbolAllocation);
if (a.symbolAllocation(1) + a.symbolAllocation(2) > 14)
eidType = 'srsChEstimatorUnittest:characterize';
msgType = 'Inconsistent symbol allocation.';
throwAsCaller(MException(eidType, msgType));
end
if ~isfield(a, 'dmrsOffset')
eidType = 'srsChEstimatorUnittest:characterize';
msgType = 'Missing configuration field "dmrsOffset".';
throwAsCaller(MException(eidType, msgType));
end
mustBeScalarOrEmpty(a.dmrsOffset);
mustBeMember(a.dmrsOffset, [0, 1]);
if ~isfield(a, 'dmrsStrideSCS')
eidType = 'srsChEstimatorUnittest:characterize';
msgType = 'Missing configuration field "dmrsStrideSCS".';
throwAsCaller(MException(eidType, msgType));
end
mustBeScalarOrEmpty(a.dmrsStrideSCS);
mustBeMember(a.dmrsStrideSCS, [1, 2, 3]);
if ~isfield(a, 'dmrsStrideTime')
eidType = 'srsChEstimatorUnittest:characterize';
msgType = 'Missing configuration field "dmrsStrideTime".';
throwAsCaller(MException(eidType, msgType));
end
mustBeScalarOrEmpty(a.dmrsStrideTime);
mustBeMember(a.dmrsStrideTime, [1, 2, 4, 6, 20]);
if ~isfield(a, 'betaDMRS')
eidType = 'srsChEstimatorUnittest:characterize';
msgType = 'Missing configuration field "betaDMRS".';
throwAsCaller(MException(eidType, msgType));
end
mustBeScalarOrEmpty(a.betaDMRS);
mustBeMember(a.betaDMRS, [-3, 0]);
end
function crlb = computeCRLB(prbMask, reMask)
%computeCRLB Cramer-Rao Lower Bound
% CRLB = computeCRLB(PRBMASK, REMASK) computes the Cramer-Rao Lower Bound (CRLB)
% for the channel estimation. The CRLB is computed assuming that the entire band
% can be used for the estimation, with pilots spaced according to REMASK (first
% entry) or with pilots in all REs (second entry). The assumption is needed to
% avoid a singular Fisher matrix.
Nprb = length(prbMask);
Nre = Nprb * 12;
assert(length(reMask) == 12);
E = diag(kron(ones(Nprb, 1), reMask));
Jbig = ifft(fft(E, Nre, 2), Nre, 1);
cp = floor(Nre / 10);
J = Jbig(1:cp, 1:cp);
s = warning('error', 'MATLAB:nearlySingularMatrix');
crlb = nan(2, 1);
chMask = (kron(prbMask, ones(12, 1)) == 1);
try
C = inv(J);
M = fft(ifft(C, Nre, 2), Nre, 1);
crlb(1) = real(trace(M(chMask, chMask))) / sum(chMask);
catch ME
if strcmp(ME.identifier, 'MATLAB:nearlySingularMatrix')
warning('Pattern CRLB can''t be computed.');
else
rethrow(ME);
end
end
E = diag(kron(ones(Nprb, 1), ones(12, 1)));
Jbig = ifft(fft(E, Nre, 2), Nre, 1);
J = Jbig(1:cp, 1:cp);
try
C = inv(J);
M = fft(ifft(C, Nre, 2), Nre, 1);
crlb(2) = real(trace(M(chMask, chMask))) / sum(chMask);
catch ME
if ~strcmp(ME.identifier, 'MATLAB:nearlySingularMatrix')
warning('Full CRLB can''t be computed.');
else
rethrow(ME);
end
end
warning(s);
end